The present invention relates generally to packaging technique, and the invention relates in particular to a novel and unique sealing method as well as a seal or closure for containers, especially plastic bottles.
Several different types of containers are already known and many of them have various drawbacks. Glass bottles for instance have among other things the drawbacks of being easily crushed, and exhibiting relatively large weight as well as relatively high material cost. Containers manufactured of paper, for instance those provided with waxed or plastic coated surfaces, have the drawbacks among other things that they are easily deformable, they are easy to damage and they are incapable of being treated in connection with certain processes, for instance sterilization of the contents thereof. Then there are plastic bottles, and the invention relates to this type of container. Among the advantages of plastic bottles, their low weight, capability to withstand crushing and relatively low manufacturing cost could be mentioned. A drawback of plastic containers is their heat sensitiveness due to the inherent characteristics of the plastic material, and due to this fact, for instance deforming may occur in connection with heating and subsequent cooling. Another problem is faced in connection with obtaining a suitable seal or closure. Plastic bottles have often been sealed by a plastic cap being slightly depressable into the throat of the plastic bottle and then being maintained in place by a press fitting and the frictional engagement. Such seal requires an outer cover, generally made of a metallic strip, provided on top of the plastic cap and the upper portion of the bottle throat. Previously used sealing methods and closures manufactured have been relatively expensive and time demanding, and some other drawbacks have also been encountered. It has for instance not always been possible to guarantee with certainty that a leakage will not occur and that air, germs or the like would reach the contents of the bottle and contaminate the same.